1. Field of the Invention
This invention relates to the purification of anthocyans, and, more especially, relates to the purification of aqueous solutions of anthocyans by contacting same with a certain, polystyrene coated metal oxide adsorbent, and thence by separating the adsorbent and treating it with an eluant.
2. Description of the Prior Art
Anthocyans are natural red, blue and violet food colorants which cannot be obtained in powder form from their solutions of extraction because of the impurities contained in such solutions. In order to purify these solutions, it has to date been proposed to treat the aqueous solutions of extraction with adsorbents such as talc, which adsorbents adsorb the anthocyans, which are then subsequently eluted with an aqueous solution of sulfur dioxide or alcohol. However, talc has but slight capacity for such adsorption and, therefore, it is necessary to use large amounts of the talc; moreover, it is difficult to separate talc from aqueous suspensions thereof and any continuous separation technique is virtually impossible due to the low granulometry of the talc.
It has also been proposed to adsorb anthocyans on various anion exchangers, but such adsorption lacks selectivity and subsequent elution must be performed at a pH which is harmful to the quality of the resultant desired product.